The present invention relates to a technology effective in an application to a-LAN emulation technology in an ATM communication network.
A system for actualizing a LAN emulation in an ATM network involves a data transmission between LAN emulation terminals connected to an ATM switch via the ATM network. Connected to the ATM switch are a group of servers for actualizing a LAN emulation function such as, e.g., a LAN emulation server (LES), a Broadcast and Unknown Server (BUS) and a LAN emulation configuration server (LECS).
If a fault occurs in the server group for the LAN emulation, it follows that a trouble is caused in communications between LAN emulation clients. In the great majority of cases, there exists only one system of the LAN emulation configuration server (LECS) in the network, and, if the fault occurs in this LECS, there must be a high possibility in which the whole network might fall into a system-down.
There can be considered the following contrivances for avoiding the above system-down.
(1) An implementation system, i.e., the server group for providing the LAN emulation service function is constructed as a dual structure.
(2) The implementation system for providing the LAN emulation service function incorporates a line dual function.
(3) The ATM switch itself incorporates the line dual function.
In the above contrivances (2) and (3), it is required that the dual function based on the same procedures be incorporated into the implementation system (the server group) connected to an opposite equipment, i.e., the ATM switch existing on the opposite side and therefore be incorporated at a plurality of places. This conduces to a problem in which the incorporation of the function itself becomes heavy.
Accordingly, it is considered optimal to adopt the contrivance (1), however, there has been made no examination about a concrete method of actualizing it.
It is a primary object of the present invention, which was contrived in view of the point described above, to provide a LAN emulation system capable of avoiding a fault without making the line dual by a local dual structure on the premise that a LAN emulation server is made dual.